This invention relates generally to vehicle tire pressure control systems, and more particularly relates to a system for transmitting power to an aircraft tire pressure sensor from a control unit associated with a wheel hub and transmitting data between the aircraft tire pressure sensor and the control unit. The invention pertains more specifically to a communication link between a tire pressure sensor on a wheel rim and a wheel hub axle transformer for communication with control electronics, particularly for aircraft.
It is useful in an airplane to measure the pressure of each tire with a tire pressure sensor on a wheel rim, and display the tire pressure sensor information in the cockpit. It is necessary to communicate this information from the tire pressure sensor on the wheel rim to a wheel hub axle transformer, from the wheel hub axle transformer to an electronics interface circuit located in an electronics bay of the aircraft inside the pressurized vessel, which can typically be up to about 250 feet away from the tire pressure sensor, and then from the electronics bay to the cockpit.
One known tire pressure system uses a pair of transformer coils to communicate between a primary and secondary coil in the wheel axle. These transformers are coaxial and face each other. A length of wire connected to the secondary of the transformer pair connects directly with the tire pressure sensor that is located on the periphery of the wheel rim. Another known device for enhancing the magnetic coupling in a RFID wireless communication system includes first and second antenna coils connected together by electrical connectors in a closed loop and formed on a flexible substrate that can be folded around a magnetic flux blocker to avoid magnetic interference from the magnetic flux blocker.
However, it is desirable to provide communication between an airplane wheel hub and a tire pressure sensor located on the rim of the wheel up to nine inches away from the wheel hub without using electrical connections that can be unreliable and easily be broken in a harsh airplane wheel environment. It is thus desirable to provide a non-contact method of communication between an airplane wheel hub and a tire pressure sensor located on the rim of the wheel that does not require electrical connections or a length of wire to communicate between the wheel hub and the tire pressure sensor.
A magnetically coupled antenna range extender is also known that is structured to be interposed between an RF antenna and an electronic device from 0.5 to 5 centimeters from the RF antenna or the electronic device, for extending the operating range of communication between the RF antenna and the electronic device. The antenna range extender includes a passive series tuned resonate circuit that must be tuned to resonate substantially at the frequency of an RF signal radiated by the RF antenna. The passive series tuned resonate circuit can be formed by an open loop coil of an electrical conductor, with a capacitor connected in series and completing the circuit. However, it has been found that an electromotive force can be induced in such a loop by stray magnetic flux that can generate an electric current that can interfere with a desired signal being conducted.
A passive radio-frequency transmission device for increasing the transmission efficiency of radio-frequency systems is also known that includes a transmission antenna, a receiving antenna, and one or more passive resonant circuits positioned between the transmission and receiving antennas.
A need therefore remains to reduce the cost of the device that links the two coils, and to reduce the complexity of the device that links the magnetic field, in a manner that avoids the generation of signal interference, the use of unreliable electrical connections, and the use wires for electrical connections, which can easily break in the harsh environment of the airplane wheel.
It would be desirable to provide such a system that minimizes the use of direct electrical connections or a length of wire to communicate tire pressure sensor information between a wheel hub coil and a tire pressure sensor at the edge of the tire rim from an electronics interface circuit card that is located up to 250 feet away from the wheel. It would be desirable for such a system to require no more than a single turn of stamped sheet metal to couple enough magnetic flux to power and communicate with a tire pressure sensor receiver coil. It would be desirable for such a system to be substantially symmetric, with a coaxial arrangement of an axle transformer coil pair to avoid interference from airplane axle and wheel vibration. It also would be desirable for such a system to allow a sensitive electronics interface circuit card to be placed a sufficient distance away from airplane axle and wheel vibration in a benign environment of an aircraft electronics bay, typically inside a pressurized and temperature controlled vessel, for example.
It would be desirable for such a system to provide communication and power transfer through a magnetic field coupling the tire pressure sensor and the wheel axle coil. It would be desirable for such a system to be a resonant link requiring a single capacitance value for a resonant tuning capacitor, to allow such a system to work with up to 250 feet of aircraft cabling, so that the electronics interface card can work with any aircraft size or wheel configurations. The present invention fills these and other needs.